This invention relates to an improved system for the automatic recovery of play between a worm and worm gear.
It has sometimes been found that, when a rotating member, for example, a worm mechanism has to transfer its rotary movement to another member connected thereto, for example, a worm gear, particularly a worm gear carrying heavy loads, the phenomenon of wear and deformation of the contacting surfaces between the rotary members is accentuated, sometimes in such an evident manner that the exact position of the operating means, which may be connected thereto, is modified and shifted.
In particular, in industrial processes using robots--particular reference is made here to welding robots and general universal manipulators--it is of extreme importance to maintain, even after a great number of operating cycles on successive parts, the greatest possible accuracy of positioning of the operating unit at the working points contemplated in the design phase and required by the working cycle.
Although the systems that are at present used in mechanical engineering to recover the wear or deformation between a worm and worm wheel are relatively reliable, they have the great drawback that they are at the same time also considerably complex and expensive, above all because of the great number of components used for making the system.
Further, the known systems normally act substantially on the axis of the worm, pushing it and keeping it constantly in engagement with the teeth of the worm gear by hydraulical or mechanical pushing means. Although at first sight these systems may appear to be efficient, in reality they cause rapid wear of the contacting surfaces and thus necessitate a more frequent replacement of the gears.
It is an object of the present invention to provide a system that is capable of recovering the wear occurring on the contacting surfaces between the meshing teeth of a worm and worm gear and at the same time can make up for the play that may be produced by a geometric deformation of the worm gear, so that when the aforementioned drawbacks occur, the member connected to the worm gear can nevertheless always assume exact angular positions.
Finally, but certainly not less important, the system must be such that it can be easily manufactured and must be of very reduced cost.
In other words, the invention reverses the general concept of recovery of the play between a worm and worm gear by providing a system adapted to maintain constantly equal relative to one another a repetitive sequence of angular displacements made by the worm gear so as to obtain a precise reproducibility of positioning, all to the advantage of the quality of the product being machined.